User Manual

Antenna extension cable with an SMA
connector at one end and an N-type
male connector at the other end. This
cable typically connects between the
SureCross
®
device and the antenna or
another extension cable.
Antenna extension cable with an N-
type male connector at one end and an
N-type female connector at the other
end. This extension cable connects
between another cable and a surge
protector or antenna.
Surge suppressors mount between the
antenna and the radio system to
protect the electrical equipment from
damage during a lightning strike or
other electrical surge. No surge
suppressor can absorb all lightning
strikes. Do not touch any radio device
or any equipment connected to the
radio device during a thunderstorm.
CAUTION: Always install and properly ground a qualified surge suppressor when installing a remote
antenna system. Remote antenna configurations installed without surge suppressors invalidate the
Banner Engineering Corp. warranty. Always keep the ground wire as short as possible and make all
ground connections to a single-point ground system to ensure no ground loops are created.
Antenna Gain
The antenna’s gain, measured in decibels, relates directly to the radio signal’s radiation pattern and range.
Adding gain to a radio system does not amplify the signal. Antennas with greater gain only focus the signal. A low-gain
antenna transmits (and receives) the radio signal equally in all directions. A high-gain antenna transmits its signal farther
in one direction than the low-gain system.
Decibels
Mathematical equations indicate that for every 3 dB increase in the gain, the effective transmission power doubles.
Experimentation indicates that for every 6 dB increase in the gain, the radio signal range doubles. Therefore, if a 0 dB
antenna (unity gain) transmits three miles, a 6 dB antenna on the same radio transmits the signal six miles.
To simplify conversions between dBi, dBm, dBd, use the following approximation: dBm = dBi = dBd + 2.15, where
dBm refers to a ratio of the measured power referenced to 1 milliWatt, dBi is a measurement of an antenna’s gain
compared to a mathematically ideal isotropic antenna, and dBd is a ratio of the antenna’s forward gain to a half-wave
dipole antenna.
Why Do You Need Gain?
According to rules set by the FCC, radio systems like the SureCross
®
radio device may not exceed 30 dBm Effective
Isotopic Radiated Power (EIRP), or approximately 1 Watt. Because the 900 MHz SureCross radio system has a conducted
power of 21 dBm (150 mW), the maximum system gain that may be used with the Banner system is 9 dBm. Using these
higher gain antennas allows users to focus the signal both for transmission and for reception.
For systems requiring cables and connectors, the losses from the cables and connectors add up to reduce the effective
transmission power of a radio network. What starts out as a 9 dB antenna may only have an effective gain of 5 dB once
losses are totaled. Because the 9 dB limit applies to the radio system, including connectors and cables, using a higher gain
antenna may be necessary to transmit the required distance and would still comply with FCC regulations.
In addition to increasing the range, adding gain changes the radiation pattern. How the radiation pattern changes depends
on the type of antenna: omni-directional or directional.
Line of Sight
Accurate radio transmission depends on a clear path between radio antennas known as the line of sight.
Obstructions, including buildings, trees, or terrain, that interrupt the visual path between antennas also interfere with the
radio signal transmission, resulting in multi-path fade or increased signal attenuation. Multi-path fade is the result of
radio signals reaching the receiver via two or more paths. In industrial settings, received radio signals may include the line
of sight signal and signals reflected off buildings, equipment, or outdoor terrain. Signal attenuation is the decrease in
signal strength as a result of travel through the medium, in this case the air.
Antenna Basics
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